1. Field of the Invention
This invention relates to a legged mobile robot, particularly to a legged mobile robot that enables removal of static electric charge electrified or accumulated in the robot's feet by electrical discharge.
2. Description of the Related Art
Japanese Laid-Open Patent Application No. Hei 9(1997)-94785 teaches a legged mobile robot. The legged mobile robot of this reference has a body, two legs connected to the body, and feet connected to the distal ends of the legs through ankle joints. Each leg is equipped with at least an electric motor for driving a second joint between the foot and leg and a force sensor that detects floor reaction force acting on the robot from the floor surface contacted by the foot. The feet of this legged mobile robot are composed of flat frames made of aluminum, for example, and elastic member made of cushioning material such as urethane rubber, adhered to the soles of the feet for absorbing the impact produced when the feet make contact with the floor.
When such a legged mobile robot moves across a floor, static electric charge (static electricity) may accumulate in the robot owing to friction between the elastic member and the floor and/or friction between the links constituting the legs and the like. Japanese Laid-Open Utility Model Application No. Hei 6 (1994)-09098, Japanese Laid-Open Patent Application No. Hei 11(1999)-138488 and Japanese Laid-Open Patent Application No. 2001-267094 teach techniques for discharging electrified static electric charge. The second reference '098 teaches an automatic guided (unmanned) vehicle equipped with a contacting device (discharging device) that comprises contact plates, contacts and conductors and operates to equalize the potential of the charge electrified on the vehicle and that of the facility bearing the workpiece. The third reference '488 and fourth reference '094 are similarly directed to removal of the charge electrified in a fixed industrial robot by discharging it.
In legged mobile robots, since the electrified static electric charge, when large in terms of amount of energy, may sometimes acts as noise for force sensors if the sensors are mounted at a location just above the feet, the electrified charge should preferably be discharged and removed. However, the second to fourth references merely disclose discharging or removing the charge electrified on the unmanned vehicle or industrial robots and suggest nothing for the legged mobile robots.